A variety of perspectives by geologists about science, politics, religion and other things geologists like.

Sunday, February 26, 2006

The fossil record

In 2001 a friend of mine gave me a book titled "Studies in Flood Geology" authored by John Woodmorappe, and published by the Institute for Creation Research in 1999. The book is a compilation of some of the papers that Woodmorappe wrote from the late 70s through the early 90s.

The book covers a wide range of topics trying to 1) reconcile the geologic record with Noah's Flood and 2) show problems with conventional geology. For example, one chapter is titled "The Cephalopods in the Creation and the Universal Deluge", while another is titled "The Antediluvian Biosphere and its Capability of Supplying the Entire Fossil Record." My favorite is "The Essential Nonexistence of the Evolutionary-Uniformitarian Geologic Column: A Quantitative Assessment."

I'm going to address "An Anthology of Matters Significant to Creationism and Diluviology: Report 2. Section IV. Some Examples of "Reworking" Rationalizations for Anomalous Fossils." In that entry Woodmorappe compiles a list of 232 anomalous fossils (fossils that are found in rocks that are either too old or too young – a trilobite in Tertiary strata, for example.) Woodmorappe has a table that lists a) the type of fossil, b) its expected age, c) its actual age, d) the geographic location, and e), the reference. Woodmorappe has a well-deserved reputation for having a lot of references. That doesn't imply anything about the quality of his work, but at least he is thorough. I'm going to take a look at the data in a few different ways.

As you can see 93% of the anomalous fossils reported by Woodmorappe are microfossils. More on this later.

Next I want to take a look at the types of anomalous fossils.

Most of the anomalous fossils are spores, pollen, conodonts, forminifera, and and acritarchs. Most of the rest of the fossils have, at most, a few reported anomalous occurrences.

Here's the final way of looking at the data. The following graph shows how far from their expected range the anomalous fossils are found.

Positive numbers mean a fossil is found in younger than expected rocks. Negative numbers mean that a fossil is found in older than expected rocks. The numbers denote the number of periods the fossil is "out of order." For example a Cretaceous fossil found in Tertiary rocks would have a value of +1 while a Silurian fossil found in Cambrian rocks would have a value of -2.

Putting it all together:

1) Most of the anomalous fossils are microfossils.

2) Most of those microfossils are spores, pollen, conodonts, foraminifera, and acritarchs.

3) Most of the anomalous fossils are younger than expected, and most of those are younger by one Period.

Woodmorappe discusses a few of these observations. For example concerning the prevalence of microfossils he says:

"Reworked" and "downwashed" forms are microfossils, it is claimed, because such small forms are resistant to erosion, transport, etc. However, many entries in Tale 1 (References omitted) involve macrofossils."

and

Another explanation is provided by the Creationist-Diluvialist paradigm. Microfossils, being minute, would be less capable of differential escape and be less subject to Flood-water sorting than macrofossils. The common situation of anomalously-occurring pollen and spores may be evidence that all fossil plants were mutually contemporaneous (as indeed demanded by the Creationist-Diluvialist paradigm) but that pollen and spores, being modile, were transported bu wind and water far beyond the restricted ecological zones of these antediluvian plants.

Concerning the observation that most of the anomalous fossils are younger than expected Woodmorappe says:

In an anomalous coexistence of fossils of different "ages", it is usually assumed that the younger fossils yield the true age of the rock rather than the older ones. This accounts for the relative paucity of "downwash" situations.

"Reworking" refers to the process by which fossils are eroded out of existing rocks. For example, if you were to go up to a Jurassic formation that current exposed at the surface, and were to look at the material that's been eroded from that rock (sand, for example), that material would contain pieces of fossils that had been weathered from the Jurassic rock. To get a little more specific, if you were to go to places where the Morrison formation is exposed (the formation that contains the dinosaurs featured at Dinosaur National Monument), and to look at the sediments that are being weathered from that formation, you may see fragments of dinosaur bones. You'd be making a mistake if you assumed the fragments of dinosaur bone you saw were from a dinosaur that had died recently. To be fair, Woodmorappe does acknowledge this possibility:

This table does not include fossils of clearly secondary position (such as fossils within constituents of conglomerates and the very many instances of Phanerozoic fossils in Pleistocene glacial till).

But he doesn't say whether or not it includes finding fragmentary fossils, and he really should. Finding a fragmentary fossil certainly doesn't automatically mean that it's been reworked – I've seen plenty of fossiliferous rocks that are composed of broken-up shells, for example. That seems like a really important piece of information to me. I'd like to know, for example, if the anomalous trilobites were composed of intact animals, or if they were just fragments. I'm a little leery of some of Woodmorappe's examples. The most common crinoid (sea lily) fossils, for example, are the small discs that made up their stem. I've seen Mississippian rocks that are composed almost entirely of crinoid stems. Unsurprisingly the detritus that's being eroded from those rocks was composed in large part of crinoid stems. If those same crinoid-bearing rocks were to have been eroded during the Cretaceous (as was the case in parts of Utah, for example), then the Cretaceous rocks would contain crinoid stems. Some reworking should be expected. One or two examples of an anomalous fossil (which are all Woodmorappe has shown for most fossils) aren't evidence of a lack of order in the fossil record.

Some of Woodmorappe's examples are in a part of the world I'm familiar with. Here are a few specific examples from Woodmorappe's table that I think are legitimate reworked fossils:

Cretaceous forams found in Tertiary sediments in Utah.Cretaceous forams found in Pleistocene (Quaternary) sediments in Utah.Carboniferous fusilinds found in Pleistocene sediments in Utah.Late Paleozoic trilobite found in Tertiary sediments in Utah.

The reason why I think these are reworked is that there aren't any Tertiary marine sediments in Utah, particularly not in the Pleistocene, which was the epoch immediately before the Holocene, which is the epoch we're in now. The geology of Utah in the Pleistocene was basically the same as today, but covered with glaciers from time to time, and a large lake (Lake Bonneville – but that lake wasn't exactly teeming with trilobites – I don't know of any trilobite fossils that were found in Lake Bonneville sediments).

Here are a few other entries that I'm suspicious of:

Cretaceous pollen in Tertiary sediments in Utah and Wyoming.Jurassic pollen in Tertiary sediments in Utah.Triassic pollen in Tertiary sediments in Utah.Carboniferous pollen in Cretaceous sediments in Montana and Alberta.

The reason I'm suspicious of these examples is that the Cretaceous and Tertiary in western North America were times of mountain building, and associated with that uplift and erosion of older rocks, including Carboniferous, Triassic, Jurassic, and Cretaceous rocks. The evidence includes 1) thrust faults that formed during this time, and 2) thick conglomerates composed of clasts derived from those Carboniferous, etc., rocks that were deposited during this time. Woodmorappe does say that he didn't include fossils from conglomerates, but here's the problem with that. Conglomerates are deposited near areas that are being uplifted, grain size decreases as you move away from that area. For example, a conglomerate can be deposited at the foot of mountain, while a sandstone is deposited further away (it's easier to move smaller particles than large ones). That sandstone can certainly contain fragments of older rocks (including fossils). I expect Tertiary rocks in western North America to contain material derived from older rocks.

"Down working" refers to younger fossils becoming incorporated into older rocks. I'd expect some of this too. Keeping with the example of western North America, in the Cretaceous when the uplift and erosion I mentioned earlier was occurring, the older rocks that were being eroded (let's say Carboniferous rocks), were exposed at the surface. If some Cretaceous pollen were to be deposited on top of those rocks, and then buried once erosion stopped and deposition began again, and some geologist came along at some point in the distant future and took a sample that sample would contain Cretaceous pollen. I'd expect this scenario to be a lot less common than reworking, and I'd expect it to involve microfossils (I have a hard time imaging how an entire dinosaur could be incorporated in Carboniferous rocks for example), and that's what's seen.

In other words anomalously young fossils ought to be a lot more common than anomalously old fossils, and that's overwhelmingly the case with Woodmorappe's dataset. He tires to explain this by stating that the age of a rock is determined by the youngest fossil within it. An implication of that claim is that rocks are composed of fossils with a variety of different ages, and that implication doesn't hold true. From the third figure I showed, most fossils are displaced by only one period. If the fossils had a wide range of different ages then there ought to be a lot more scatter. At this point it's worth reemphasizing the point that most of Woodmorappe's anomalous fossils are composed of spores and pollen. So, the bulk of Woodmorappe's dataset is composed of spore and pollen that are one period younger than expected. At worst (or at best from a YEC point of view) all Woodmorappe's dataset does is muddy the conventional fossil record of spores and pollen (this is a good point for a reminder that I think most/all of Woodmorappe's references are legitimate cases of reworking).

I should point out that I haven't read Woodmorappe's references. I suppose it's possible that the answers to some of my questions are contained within them. In the part of the world that I'm most familiar with though, Woodmorappe's dataset isn't very solid.

I think the thing about science that religious people have the hardest time understanding is that there is no expectation of completeness or infallibility in science. Science doesn't have to be perfect to be good science. It just has to work better than the previous paradigm.